【聲明】
(1) 本文源碼
在一位未署名網友源碼基礎上,利用Qt編程,實現了AES加解密算法,並添加了文件加解密功能。在此表示感謝!該源碼僅供學習交流,請勿用於商業目的。
(2) 圖片及描述
除圖1外,圖片及部分解析來自http://zh.wikipedia.org/wiki/%E9%AB%98%E7%BA%A7%E5%8A%A0%E5%AF%86%E6%A0%87%E5%87%86。圖1為個人勞動成果,請勿盜用此圖。
【簡介】
AES(Advanced Encryption Standard,高級加密標准),於2001年11月26日發布於FIPS PUB 197,並在2002年5月26日成為有效的標准。2006年,高級加密標准已然成為對稱密鑰加密中最流行的算法之一。
【算法描述】
AES的區塊長度固定為128 比特,密鑰長度則可以是128,192或256比特。AES加密過程是在一個4×4的字節矩陣上運作,這個矩陣又稱為“體(state)”,其初值就是一個明文區塊(矩陣中一個元素大小就是明文區塊中的一個Byte)。加密時,各輪AES加密循環(除最后一輪外)均包含4個步驟: 1.AddRoundKey — 矩陣中的每一個字節都與該次輪密鑰(round key)做XOR運算;每個子密鑰由密鑰生成方案產生。 2.SubBytes — 通過一個非線性的替換函數,用查找表的方式把每個字節替換成對應的字節。 3.ShiftRows — 將矩陣中的每個橫列進行循環式移位。 4.MixColumns — 為了充分混合矩陣中各個直行的操作。這個步驟使用線性轉換來混合每內聯的四個字節。 最后一個加密循環中省略MixColumns步驟,而以另一個AddRoundKey取代。 AES算法加解密流程如圖1所示:
圖1 AES加密算法流程圖
【算法解析】
1 常量定義
S-Box
- const unsigned char AES::Sbox[16*16]=
- {// populate the Sbox matrix
- /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
- /*0*/ 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
- /*1*/ 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
- /*2*/ 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
- /*3*/ 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
- /*4*/ 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
- /*5*/ 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
- /*6*/ 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
- /*7*/ 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
- /*8*/ 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
- /*9*/ 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
- /*a*/ 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
- /*b*/ 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
- /*c*/ 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
- /*d*/ 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
- /*e*/ 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
- /*f*/ 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
- };
const unsigned char AES::Sbox[16*16]= {// populate the Sbox matrix /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /*0*/ 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, /*1*/ 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, /*2*/ 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, /*3*/ 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, /*4*/ 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, /*5*/ 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, /*6*/ 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, /*7*/ 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, /*8*/ 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, /*9*/ 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, /*a*/ 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, /*b*/ 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, /*c*/ 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, /*d*/ 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, /*e*/ 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, /*f*/ 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
- const unsigned char AES::iSbox[16*16]=
- {
- // populate the iSbox matrix
- /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
- /*0*/ 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
- /*1*/ 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
- /*2*/ 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
- /*3*/ 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
- /*4*/ 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
- /*5*/ 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
- /*6*/ 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
- /*7*/ 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
- /*8*/ 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
- /*9*/ 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
- /*a*/ 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
- /*b*/ 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
- /*c*/ 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
- /*d*/ 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
- /*e*/ 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
- /*f*/ 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
- };
const unsigned char AES::iSbox[16*16]= { // populate the iSbox matrix /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /*0*/ 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, /*1*/ 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, /*2*/ 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, /*3*/ 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, /*4*/ 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, /*5*/ 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, /*6*/ 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, /*7*/ 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, /*8*/ 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, /*9*/ 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, /*a*/ 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, /*b*/ 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, /*c*/ 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, /*d*/ 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, /*e*/ 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, /*f*/ 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
Rcon
- const unsigned char AES::Rcon[11*4]=
- {
- 0x00, 0x00, 0x00, 0x00,
- 0x01, 0x00, 0x00, 0x00,
- 0x02, 0x00, 0x00, 0x00,
- 0x04, 0x00, 0x00, 0x00,
- 0x08, 0x00, 0x00, 0x00,
- 0x10, 0x00, 0x00, 0x00,
- 0x20, 0x00, 0x00, 0x00,
- 0x40, 0x00, 0x00, 0x00,
- 0x80, 0x00, 0x00, 0x00,
- 0x1b, 0x00, 0x00, 0x00,
- 0x36, 0x00, 0x00, 0x00
- };
const unsigned char AES::Rcon[11*4]= { 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x08, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x1b, 0x00, 0x00, 0x00, 0x36, 0x00, 0x00, 0x00 };
2 密鑰擴展(Expand Key) AES算法利用外部輸入密鑰Key(又稱為基密鑰,密鑰串的字數為Nk),通過密鑰擴展可得到共4(Nk+1)字的擴展密鑰w[4× (Nr+1)],其中Nr為數據分組密鑰的輪數。密鑰擴展主要包括3個步驟: (1) 位置變換RotWord() 把一個4字節的基密鑰序列[a0,a1,a2,a3],左移一個字節變為[a1,a2,a3,a0]。
- void AES::RotWord(unsigned char * word,unsigned char *result)
- {
- result[0] = word[1];
- result[1] = word[2];
- result[2] = word[3];
- result[3] = word[0];
- }
void AES::RotWord(unsigned char * word,unsigned char *result) { result[0] = word[1]; result[1] = word[2]; result[2] = word[3]; result[3] = word[0]; }
(2) SubWord() 對一個4字節的輸入字[a0,a1,a2,a3],每一個字節進行S盒變換。
- void AES::SubWord(unsigned char * word,unsigned char* result)
- {
- result[0] = Sbox[ 16*(word[0] >> 4)+ (word[0] & 0x0f) ];
- result[1] = Sbox[ 16*(word[1] >> 4)+ (word[1] & 0x0f) ];
- result[2] = Sbox[ 16*(word[2] >> 4)+ (word[2] & 0x0f) ];
- result[3] = Sbox[ 16*(word[3] >> 4)+ (word[3] & 0x0f) ];
- }
void AES::SubWord(unsigned char * word,unsigned char* result) { result[0] = Sbox[ 16*(word[0] >> 4)+ (word[0] & 0x0f) ]; result[1] = Sbox[ 16*(word[1] >> 4)+ (word[1] & 0x0f) ]; result[2] = Sbox[ 16*(word[2] >> 4)+ (word[2] & 0x0f) ]; result[3] = Sbox[ 16*(word[3] >> 4)+ (word[3] & 0x0f) ]; }
(3) 變換Rcon[] Rcon[i]表示32比特字符串[xi-1,00,00,00]。
- temp[0] = (byte)( (int)temp[0] ^ (int) Rcon[4*(row/Nk)+0] );
- temp[1] = (byte)( (int)temp[1] ^ (int) Rcon[4*(row/Nk)+1] );
- temp[2] = (byte)( (int)temp[2] ^ (int) Rcon[4*(row/Nk)+2] );
- temp[3] = (byte)( (int)temp[3] ^ (int) Rcon[4*(row/Nk)+3] );
temp[0] = (byte)( (int)temp[0] ^ (int) Rcon[4*(row/Nk)+0] ); temp[1] = (byte)( (int)temp[1] ^ (int) Rcon[4*(row/Nk)+1] ); temp[2] = (byte)( (int)temp[2] ^ (int) Rcon[4*(row/Nk)+2] ); temp[3] = (byte)( (int)temp[3] ^ (int) Rcon[4*(row/Nk)+3] );
擴展密鑰的前Nk個字就是基密鑰Key;以后的字w[i]等於它前一個字w[i-1]與前第Nk個字w[i-Nk]的異或,即w[i]=w[i-1] XOR w[i-Nk]。但如果i是Nk的倍數,則w[i]=w[i-Nk] XOR SubWord(RotWord(w[i-1])) XOR Rcon[i/Nk]。
- void AES::KeyExpansion()
- {
- unsigned char result[4],result2[4];
- memset(w,0,16*15);//沒有根據key的位數進行開辟空間,直接開辟了最大空間
- int row;
- for (row = 0; row < Nk; row++)//Nk=4,6,8得到初始密碼
- {
- w[4*row+0] = key[4*row];
- w[4*row+1] = key[4*row+1];
- w[4*row+2] = key[4*row+2];
- w[4*row+3] = key[4*row+3];
- }
- unsigned char temp[4];
- for (row = Nk; row < Nb * (Nr+1); row++)//產生密匙順序表
- {
- temp[0] = w[4*(row-1)+0];
- temp[1] = w[4*(row-1)+1];
- temp[2] = w[4*(row-1)+2];
- temp[3] = w[4*(row-1)+3];
- if (row % Nk == 0)
- {
- RotWord(temp,result);
- SubWord(result,result2);
- memcpy(temp,result2,4);//
- //RotWord 例程非常簡單,它接受 4 字節的數組並將它們向左旋轉位移 1 位。
- //因為輪回次序表 w[] 有四列,所以 RotWord 會將一行 w[] 向左旋轉位移.
- //SubWord 例程使用置換表 Sbox,針對密鑰次序表 w[] 的給定行執行逐字節置換。
- temp[0] = (byte)( (int)temp[0] ^ (int) Rcon[4*(row/Nk)+0] );
- temp[1] = (byte)( (int)temp[1] ^ (int) Rcon[4*(row/Nk)+1] );
- temp[2] = (byte)( (int)temp[2] ^ (int) Rcon[4*(row/Nk)+2] );
- temp[3] = (byte)( (int)temp[3] ^ (int) Rcon[4*(row/Nk)+3] );
- }
- else if ( Nk > 6 && (row % Nk == 4) )
- {
- SubWord(temp,result);
- memcpy(temp,result,4);
- }
- // w[row] = w[row-Nk] xor temp
- w[4*row+0] = (byte) ( (int) w[4*(row-Nk)+0] ^ (int)temp[0] );
- w[4*row+1] = (byte) ( (int) w[4*(row-Nk)+1] ^ (int)temp[1] );
- w[4*row+2] = (byte) ( (int) w[4*(row-Nk)+2] ^ (int)temp[2] );
- w[4*row+3] = (byte) ( (int) w[4*(row-Nk)+3] ^ (int)temp[3] );
- } // for loop
- } // KeyExpansion()
void AES::KeyExpansion() { unsigned char result[4],result2[4]; memset(w,0,16*15);//沒有根據key的位數進行開辟空間,直接開辟了最大空間 int row; for (row = 0; row < Nk; row++)//Nk=4,6,8得到初始密碼 { w[4*row+0] = key[4*row]; w[4*row+1] = key[4*row+1]; w[4*row+2] = key[4*row+2]; w[4*row+3] = key[4*row+3]; } unsigned char temp[4]; for (row = Nk; row < Nb * (Nr+1); row++)//產生密匙順序表 { temp[0] = w[4*(row-1)+0]; temp[1] = w[4*(row-1)+1]; temp[2] = w[4*(row-1)+2]; temp[3] = w[4*(row-1)+3]; if (row % Nk == 0) { RotWord(temp,result); SubWord(result,result2); memcpy(temp,result2,4);// //RotWord 例程非常簡單,它接受 4 字節的數組並將它們向左旋轉位移 1 位。 //因為輪回次序表 w[] 有四列,所以 RotWord 會將一行 w[] 向左旋轉位移. //SubWord 例程使用置換表 Sbox,針對密鑰次序表 w[] 的給定行執行逐字節置換。 temp[0] = (byte)( (int)temp[0] ^ (int) Rcon[4*(row/Nk)+0] ); temp[1] = (byte)( (int)temp[1] ^ (int) Rcon[4*(row/Nk)+1] ); temp[2] = (byte)( (int)temp[2] ^ (int) Rcon[4*(row/Nk)+2] ); temp[3] = (byte)( (int)temp[3] ^ (int) Rcon[4*(row/Nk)+3] ); } else if ( Nk > 6 && (row % Nk == 4) ) { SubWord(temp,result); memcpy(temp,result,4); } // w[row] = w[row-Nk] xor temp w[4*row+0] = (byte) ( (int) w[4*(row-Nk)+0] ^ (int)temp[0] ); w[4*row+1] = (byte) ( (int) w[4*(row-Nk)+1] ^ (int)temp[1] ); w[4*row+2] = (byte) ( (int) w[4*(row-Nk)+2] ^ (int)temp[2] ); w[4*row+3] = (byte) ( (int) w[4*(row-Nk)+3] ^ (int)temp[3] ); } // for loop } // KeyExpansion()
3 輪密鑰加(Add Round Key) 如圖2所示,經過擴展的密鑰,根據加密的輪數用相應的擴展密鑰的4個數據項和中間狀態矩陣上的列進行按位異或:
[s(0,c)’, s(1,c)’, s(2,c)’, s(3,c)’]= [s(0,c), s(1,c), s(2,c), s(3,c)] XOR [W(round×Nb+c)]。
圖2 Add Round Key
- void AES::AddRoundKey(int round)
- {
- int r,c;
- for (r = 0; r < 4; r++)
- {
- for (c = 0; c < 4; c++)
- {//w: 4*x+y
- State[r][c]=(unsigned char)((int)State[r][c]^(int)w[4*((round*4)+c)+r]);
- }
- }
- } // AddRoundKey()
void AES::AddRoundKey(int round) { int r,c; for (r = 0; r < 4; r++) { for (c = 0; c < 4; c++) {//w: 4*x+y State[r][c]=(unsigned char)((int)State[r][c]^(int)w[4*((round*4)+c)+r]); } } } // AddRoundKey()
4 字節替代(Substitute Bytes) 如圖3所示,從S-Box中找出S[A]=S[x,y]的值,其中A為輸入矩陣任一元素。將
轉換為
圖3 Substitute Bytes
- void AES::SubBytes()
- {
- int r,c;
- for (r = 0; r < 4; r++)
- {
- for (c = 0; c < 4; c++)
- {
- State[r][c] = Sbox[ 16*(State[r][c] >> 4)+ ( State[r][c] & 0x0f) ];
- }
- }
- } // SubBytes
- void AES::InvSubBytes()
- {
- int r,c;
- for (r = 0; r < 4; r++)
- {
- for (c = 0; c < 4; c++)
- {
- State[r][c] = iSbox[ 16*( State[r][c] >> 4)+( State[r][c] & 0x0f) ];
- }
- }
- } // InvSubBytes
void AES::SubBytes() { int r,c; for (r = 0; r < 4; r++) { for (c = 0; c < 4; c++) { State[r][c] = Sbox[ 16*(State[r][c] >> 4)+ ( State[r][c] & 0x0f) ]; } } } // SubBytes void AES::InvSubBytes() { int r,c; for (r = 0; r < 4; r++) { for (c = 0; c < 4; c++) { State[r][c] = iSbox[ 16*( State[r][c] >> 4)+( State[r][c] & 0x0f) ]; } } } // InvSubBytes
5 行移位(Shift Rows) 如圖4所示,將矩陣中的每一個橫列進行循環式移位。移位的規則是:第一行維持不變,第二、第三、第四行的每個字節向左循環移位的偏移量分別為1格,2格,3格。
圖4 Shift Rows
- void AES::ShiftRows()
- {
- unsigned char temp[4*4];
- int r,c;
- for (r = 0; r < 4; r++) // copy State into temp[]
- {
- for (c = 0; c < 4; c++)
- {
- temp[4*r+c] = State[r][c];
- }
- }
- for (r = 1; r < 4; r++) // shift temp into State
- {
- for (c = 0; c < 4; c++)
- {
- State[r][c] = temp[ 4*r+ (c + r) % Nb ];
- }
- }
- } // ShiftRows()
- void AES::InvShiftRows()
- {
- unsigned char temp[4*4];
- int r,c;
- for (r = 0; r < 4; r++) // copy State into temp[]
- {
- for (c = 0; c < 4; c++)
- {
- temp[4*r+c] = State[r][c];
- }
- }
- for (r = 1; r < 4; r++) // shift temp into State
- {
- for (c = 0; c < 4; c++)
- {
- State[r][ (c + r) % Nb ] = temp[4*r+c];
- }
- }
- } // InvShiftRows()
void AES::ShiftRows() { unsigned char temp[4*4]; int r,c; for (r = 0; r < 4; r++) // copy State into temp[] { for (c = 0; c < 4; c++) { temp[4*r+c] = State[r][c]; } } for (r = 1; r < 4; r++) // shift temp into State { for (c = 0; c < 4; c++) { State[r][c] = temp[ 4*r+ (c + r) % Nb ]; } } } // ShiftRows() void AES::InvShiftRows() { unsigned char temp[4*4]; int r,c; for (r = 0; r < 4; r++) // copy State into temp[] { for (c = 0; c < 4; c++) { temp[4*r+c] = State[r][c]; } } for (r = 1; r < 4; r++) // shift temp into State { for (c = 0; c < 4; c++) { State[r][ (c + r) % Nb ] = temp[4*r+c]; } } } // InvShiftRows()
6 列混淆(Mix Columns) 如圖5所示,列變換的中間狀態矩陣State如下所示:
經過上述變換,原來的列被混淆為新列。
圖5 Mix Column
- void AES::MixColumns()
- {
- unsigned char temp[4*4];
- int r,c;
- for (r = 0; r < 4; r++) // copy State into temp[]
- {
- for (c = 0; c < 4; c++)
- {
- temp[4*r+c] = State[r][c];
- }
- }
- for (c = 0; c < 4; c++)
- {
- State[0][c] = (unsigned char) ( (int)gfmultby02(temp[0+c]) ^ (int)gfmultby03(temp[4*1+c]) ^
- (int)gfmultby01(temp[4*2+c]) ^ (int)gfmultby01(temp[4*3+c]) );
- State[1][c] = (unsigned char) ( (int)gfmultby01(temp[0+c]) ^ (int)gfmultby02(temp[4*1+c]) ^
- (int)gfmultby03(temp[4*2+c]) ^ (int)gfmultby01(temp[4*3+c]) );
- State[2][c] = (unsigned char) ( (int)gfmultby01(temp[0+c]) ^ (int)gfmultby01(temp[4*1+c]) ^
- (int)gfmultby02(temp[4*2+c]) ^ (int)gfmultby03(temp[4*3+c]) );
- State[3][c] = (unsigned char) ( (int)gfmultby03(temp[0+c]) ^ (int)gfmultby01(temp[4*1+c]) ^
- (int)gfmultby01(temp[4*2+c]) ^ (int)gfmultby02(temp[4*3+c]) );
- }
- } // MixColumns
- void AES::InvMixColumns()
- {
- unsigned char temp[4*4];
- int r,c;
- for (r = 0; r < 4; r++) // copy State into temp[]
- {
- for (c = 0; c < 4; c++)
- {
- temp[4*r+c] = State[r][c];
- }
- }
- for (c = 0; c < 4; c++)
- {
- State[0][c] = (unsigned char) ( (int)gfmultby0e(temp[c]) ^ (int)gfmultby0b(temp[4+c]) ^
- (int)gfmultby0d(temp[4*2+c]) ^ (int)gfmultby09(temp[4*3+c]) );
- State[1][c] = (unsigned char) ( (int)gfmultby09(temp[c]) ^ (int)gfmultby0e(temp[4+c]) ^
- (int)gfmultby0b(temp[4*2+c]) ^ (int)gfmultby0d(temp[4*3+c]) );
- State[2][c] = (unsigned char) ( (int)gfmultby0d(temp[c]) ^ (int)gfmultby09(temp[4+c]) ^
- (int)gfmultby0e(temp[4*2+c]) ^ (int)gfmultby0b(temp[4*3+c]) );
- State[3][c] = (unsigned char) ( (int)gfmultby0b(temp[c]) ^ (int)gfmultby0d(temp[4+c]) ^
- (int)gfmultby09(temp[4*2+c]) ^ (int)gfmultby0e(temp[4*3+c]) );
- }
- } // InvMixColumns
- unsigned char AES::gfmultby01(unsigned char b)
- {
- return b;
- }
- unsigned char AES::gfmultby02(unsigned char b)
- {
- if (b < 0x80)
- return (unsigned char)(int)(b <<1);
- else
- return (unsigned char)( (int)(b << 1) ^ (int)(0x1b) );
- }
- unsigned char AES::gfmultby03(unsigned char b)
- {
- return (unsigned char) ( (int)gfmultby02(b) ^ (int)b );
- }
- unsigned char AES::gfmultby09(unsigned char b)
- {
- return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^
- (int)b );
- }
- unsigned char AES::gfmultby0b(unsigned char b)
- {
- return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^
- (int)gfmultby02(b) ^
- (int)b );
- }
- unsigned char AES::gfmultby0d(unsigned char b)
- {
- return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^
- (int)gfmultby02(gfmultby02(b)) ^
- (int)(b) );
- }
- unsigned char AES::gfmultby0e(unsigned char b)
- {
- return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^
- (int)gfmultby02(gfmultby02(b)) ^
- (int)gfmultby02(b) );
- }
void AES::MixColumns() { unsigned char temp[4*4]; int r,c; for (r = 0; r < 4; r++) // copy State into temp[] { for (c = 0; c < 4; c++) { temp[4*r+c] = State[r][c]; } } for (c = 0; c < 4; c++) { State[0][c] = (unsigned char) ( (int)gfmultby02(temp[0+c]) ^ (int)gfmultby03(temp[4*1+c]) ^ (int)gfmultby01(temp[4*2+c]) ^ (int)gfmultby01(temp[4*3+c]) ); State[1][c] = (unsigned char) ( (int)gfmultby01(temp[0+c]) ^ (int)gfmultby02(temp[4*1+c]) ^ (int)gfmultby03(temp[4*2+c]) ^ (int)gfmultby01(temp[4*3+c]) ); State[2][c] = (unsigned char) ( (int)gfmultby01(temp[0+c]) ^ (int)gfmultby01(temp[4*1+c]) ^ (int)gfmultby02(temp[4*2+c]) ^ (int)gfmultby03(temp[4*3+c]) ); State[3][c] = (unsigned char) ( (int)gfmultby03(temp[0+c]) ^ (int)gfmultby01(temp[4*1+c]) ^ (int)gfmultby01(temp[4*2+c]) ^ (int)gfmultby02(temp[4*3+c]) ); } } // MixColumns void AES::InvMixColumns() { unsigned char temp[4*4]; int r,c; for (r = 0; r < 4; r++) // copy State into temp[] { for (c = 0; c < 4; c++) { temp[4*r+c] = State[r][c]; } } for (c = 0; c < 4; c++) { State[0][c] = (unsigned char) ( (int)gfmultby0e(temp[c]) ^ (int)gfmultby0b(temp[4+c]) ^ (int)gfmultby0d(temp[4*2+c]) ^ (int)gfmultby09(temp[4*3+c]) ); State[1][c] = (unsigned char) ( (int)gfmultby09(temp[c]) ^ (int)gfmultby0e(temp[4+c]) ^ (int)gfmultby0b(temp[4*2+c]) ^ (int)gfmultby0d(temp[4*3+c]) ); State[2][c] = (unsigned char) ( (int)gfmultby0d(temp[c]) ^ (int)gfmultby09(temp[4+c]) ^ (int)gfmultby0e(temp[4*2+c]) ^ (int)gfmultby0b(temp[4*3+c]) ); State[3][c] = (unsigned char) ( (int)gfmultby0b(temp[c]) ^ (int)gfmultby0d(temp[4+c]) ^ (int)gfmultby09(temp[4*2+c]) ^ (int)gfmultby0e(temp[4*3+c]) ); } } // InvMixColumns unsigned char AES::gfmultby01(unsigned char b) { return b; } unsigned char AES::gfmultby02(unsigned char b) { if (b < 0x80) return (unsigned char)(int)(b <<1); else return (unsigned char)( (int)(b << 1) ^ (int)(0x1b) ); } unsigned char AES::gfmultby03(unsigned char b) { return (unsigned char) ( (int)gfmultby02(b) ^ (int)b ); } unsigned char AES::gfmultby09(unsigned char b) { return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^ (int)b ); } unsigned char AES::gfmultby0b(unsigned char b) { return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^ (int)gfmultby02(b) ^ (int)b ); } unsigned char AES::gfmultby0d(unsigned char b) { return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^ (int)gfmultby02(gfmultby02(b)) ^ (int)(b) ); } unsigned char AES::gfmultby0e(unsigned char b) { return (unsigned char)( (int)gfmultby02(gfmultby02(gfmultby02(b))) ^ (int)gfmultby02(gfmultby02(b)) ^ (int)gfmultby02(b) ); }
7 AES加密 加密時,首先進行密鑰擴展。密鑰擴展的結果是將初始密鑰按照一定的移位和置換操作擴展為11組128位的密鑰,存儲在一個W[44][4]的數組里。將輸入的明文,按列順序組合成4×4的矩陣,直接與第0組密鑰W[0,3](即基密鑰Key)進行異或,作為輪加密的輸入。然后,循環10次進行字節替代(Substitute Bytes)、行位移(Shift Rows)、列混淆(Mix Columns)、輪密鑰加運算(Add Round Key)。最后一輪運算不進行列混淆變換。最后,輸出128位的密文比特流。
- void AES::Cipher(unsigned char* input, unsigned char* output) // encipher 16-bit input
- {
- // state = input
- memset(&State[0][0],0,16);
- int i;
- for (i = 0; i < (4 * Nb); i++)//
- {
- State[i % 4][ i / 4] = input[i];
- }
- AddRoundKey(0);
- for (int round = 1; round <= (Nr - 1); round++) // main round loop
- {
- SubBytes();
- ShiftRows();
- MixColumns();
- AddRoundKey(round);
- } // main round loop
- SubBytes();
- ShiftRows();
- AddRoundKey(Nr);
- // output = state
- for (i = 0; i < (4 * Nb); i++)
- {
- output[i] = State[i % 4][ i / 4];
- }
- } // Cipher()
void AES::Cipher(unsigned char* input, unsigned char* output) // encipher 16-bit input { // state = input memset(&State[0][0],0,16); int i; for (i = 0; i < (4 * Nb); i++)// { State[i % 4][ i / 4] = input[i]; } AddRoundKey(0); for (int round = 1; round <= (Nr - 1); round++) // main round loop { SubBytes(); ShiftRows(); MixColumns(); AddRoundKey(round); } // main round loop SubBytes(); ShiftRows(); AddRoundKey(Nr); // output = state for (i = 0; i < (4 * Nb); i++) { output[i] = State[i % 4][ i / 4]; } } // Cipher()
8 AES解密 解密時,進行加密過程逆運算,除輪密鑰加和密鑰擴展不變外,其余都需要進行相應的逆變換。當基密鑰正確,並且采用正確的解密算法,點擊解密,對文件進行正確解密。
- void AES::InvCipher(unsigned char * input, unsigned char * output) // decipher 16-bit input
- {
- // state = input
- int i;
- memset(&State[0][0],0,16);
- for (i = 0; i < (4 * Nb); i++)
- {
- State[i % 4][ i / 4] = input[i];
- }
- AddRoundKey(Nr);
- for (int round = Nr-1; round >= 1; round--) // main round loop
- {
- InvShiftRows();
- InvSubBytes();
- AddRoundKey(round);
- InvMixColumns();
- } // end main round loop for InvCipher
- InvShiftRows();
- InvSubBytes();
- AddRoundKey(0);
- // output = state
- for (i = 0; i < (4 * Nb); i++)
- {
- output[i] = State[i % 4][ i / 4];
- }
- } // InvCipher()
void AES::InvCipher(unsigned char * input, unsigned char * output) // decipher 16-bit input { // state = input int i; memset(&State[0][0],0,16); for (i = 0; i < (4 * Nb); i++) { State[i % 4][ i / 4] = input[i]; } AddRoundKey(Nr); for (int round = Nr-1; round >= 1; round--) // main round loop { InvShiftRows(); InvSubBytes(); AddRoundKey(round); InvMixColumns(); } // end main round loop for InvCipher InvShiftRows(); InvSubBytes(); AddRoundKey(0); // output = state for (i = 0; i < (4 * Nb); i++) { output[i] = State[i % 4][ i / 4]; } } // InvCipher()
【算法舉例】
- void print(const char *key, unsigned char* value)
- {
- int i;
- printf("%s:\n", key);
- for(i=0; i<16; i++)
- {
- printf("%s%#x ", value[i]>15 ? "" : "0", value[i]);
- }
- printf("\n");
- }
- unsigned char input[] =
- {
- 0x32, 0x43, 0xf6, 0xa8,
- 0x88, 0x5a, 0x30, 0x8d,
- 0x31, 0x31, 0x98, 0xa2,
- 0xe0, 0x37, 0x07, 0x34
- };
- unsigned char output[16] = { 0 };
- unsigned char key[] =
- {
- 0x2b, 0x7e, 0x15, 0x16,
- 0x28, 0xae, 0xd2, 0xa6,
- 0xab, 0xf7, 0x15, 0x88,
- 0x09, 0xcf, 0x4f, 0x3c
- };
- AES aes(Bits128,key);
- //-1-
- print("Input", input);
- aes.Cipher(input,output);
- print("After Cipher", output);
- aes.InvCipher(output,input);
- print("After InvCipher", input);
void print(const char *key, unsigned char* value) { int i; printf("%s:\n", key); for(i=0; i<16; i++) { printf("%s%#x ", value[i]>15 ? "" : "0", value[i]); } printf("\n"); } unsigned char input[] = { 0x32, 0x43, 0xf6, 0xa8, 0x88, 0x5a, 0x30, 0x8d, 0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37, 0x07, 0x34 }; unsigned char output[16] = { 0 }; unsigned char key[] = { 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c }; AES aes(Bits128,key); //-1- print("Input", input); aes.Cipher(input,output); print("After Cipher", output); aes.InvCipher(output,input); print("After InvCipher", input);
【文件加密】
本文僅分析AES算法本身,不就AES文件加密進行分析。源碼中的文件加密功能僅供測試用。實際使用時,文件加密可使用多線程,要考慮加鎖、明文字節填充等問題。
【源碼下載】
http://download.csdn.net/detail/tandesir/4613524
【參考文獻】
1 http://zh.wikipedia.org/wiki/%E9%AB%98%E7%BA%A7%E5%8A%A0%E5%AF%86%E6%A0%87%E5%87%86